Serologic evidence of porcine reproductive and respiratory syndrome virus infection in farm and abattoir pigs in Nigeria

Porcine reproductive and respiratory syndrome (PRRS) is considered the most important viral disease of intensive swine production because of the severe economic losses associated with it. Generally, the disease causes reproductive failure characterized by infertility, mummifications, abortions, still-births and birth of weak piglets in sows, and respiratory distress in piglets and growing pigs. There are several studies on the occurrence of PRRS in pig herds in North America, Central and South America, Europe and Asia. However, apart from few reports from South Africa, there is lack of information on the disease in Africa. In particular, the status of PRRS in Nigeria remains largely unknown despite reports of mummifications, abortions, still-births and respiratory disorders in pig herds in the country. Hence, we conducted a serological survey in pig farms and abattoirs in Lagos and Oyo states, southwest Nigeria to determine the prevalence of the disease.

368 pig sera (162 males, 206 females) collected between May, 2014 and July, 2015 were screened using a commercial enzymelinked immunosorbent assay (ELISA) kit designed to detect antibodies to both genotypes (types 1 and 2) of PRRS virus (PRRSV). The sampled pigs were observed for clinical symptoms and the farmers interviewed on herd health history.

An overall PRRSV antibody prevalence of 53.8% (198/368) was obtained. Group seroprevalence was 58.6% (95/162) and 50.0% (103/206) for farm and abattoir pigs, respectively while there was a significant difference in seropositivity between pigs from Lagos (89.4%) and Oyo (48.6%) states. Common clinical symptoms observed, especially on the farms, include loss of appetite, fever, lethargy, emaciation, nasal and ocular discharges, enlarged lymph nodes, wobbly gait, paddling movement, variation in litter size, respiratory distress and history of piglet deaths shortly after birth.

Since pigs are currently not vaccinated against PRRS in Nigeria, the findings of this study suggest that the sampled pigs were infected with PRRSV. Considering the persistent nature of the virus and its reputation as a cause of severe economic losses in the swine industry, our findings necessitate continuous surveillance for the disease among pig herds in Nigeria. This will help to ascertain the actual burden and increase awareness of the disease in order to facilitate its early detection. Among other control measures, the introduction of pigs of unknown serological status into breeding herds should be discouraged. Also, further studies to isolate and identify PRRSV strains circulating in Nigeria are advocated.

Disclosure of Interest: None Declared.